Some people have use it, some people are against it.... and I'm one of them.
At the stage your fry are ok to eat this is the the very first few days after free swimming and I think if you have plants and you tank is well lit it's completely unnecessary because the plants will produce infusoria and all other kinds of critters your fish will feed from for $0.
You also want to supplement the infusoria with microworms. By the end of the week they will be big enough to graduate to bbs.

Yuou can still "make" infusoria. Just put some lettuce in a jar with some tank water and place under a bright light or a sunny window. Leave for a week or so and you should start to see tiny critters in the water. Then you just pour some of that water in the tank with your fry everyday.